Modular hydraulic fluid supply pump



Dec. 8, 1970 G. BOBST Mommy-AR HYDRAULic FLUID SUPPLY PUMP 3 Sheets-Sheet 1 Filed N'oyt 22-3-19 8 TNVENTOR: GEM/n29 80857" ATTORNEY} Dec. 8, 1970 G. BOBST MODULAR HYDRAULIC FLUID SUPPLY PUMP 25 Sheets-Sheet 2 Filed Nov. 22. 1968 Dec. 8, 1970 I BQBST 3,545,898

MODULAR HYDRAULIC FLUID SUPPLY PUMP Filed Nov. J22, 1968 3 Sheets-Sheet 5 Flip. 39

United States Patent 3,545,898 MODULAR HYDRAULIC FLUID SUPPLY PUMP Gerhard Bobst, Oensingen, Switzerland, assignor to Von Roll A.G., Gerlafingen, Switzerland, a corporation of Switzerland Filed Nov. 22, 1968, Ser. No. 778,198 Claims priority, application Switzerland, Nov. 30, 1967, 16,826/ 67 Int. Cl. F04c /00, 1/08 US. Cl. 418-39 4 Claims ABSTRACT OF THE DISCLOSURE A group of aligned, stacked plates carry a gear pump unit at an intermediate plate, with openings for supply of fluid arranged along an axis of symmetry so that by reversing the plate carrying the gears of the pump, and turning associated plates carrying fluid ducts, about the axis of symmetry, different directions of rotation of the drive to the pump can be accommodated, and the modular unit readily associated at an inlet supply pump to a pressure pumping system.

The present invention relates to a hydraulic fluid supply pump, and more particularly to a supply pump adapted to supply hydraulic fluid to a pressure pumping system having reciprocating pistons operated by a wobble plate and requiring some pressure at the inlet side for the pressure pump.

Hydraulic pressure pumps operating at high speed, for example pumps in which a plurality of pistons slide back and forth in cylinder openings arranged co-axially around a shaft, with a wobble plate operating the pistons, require a certain amount of pressure at the suction opening. The efliciency of such pumps increases with increasing operating speed. Since the hydraulic fluid, for example oil, must fill the pumping cylinder during the suction stroke, the limit of pumped output will be reached when the speed of operation is increased to the point that fluid can no longer completely fill the cylinder. The limit of speed of pumping is usually below the limit of operating speed which can be obtained from the pumping units.

It has been proposed-to increase the output of such pressure pumps by providing an auxiliary pump that supplies fluid already under some pressure to the inlet, or suction side of the pressure pump. Pressure can be applied to the inlet line by various ways; it has been proposed to apply a compressed air cushion bearing against the inlet fluid reservoir. This solution is undesirable when the pressure pump is to be used in vehicles, and in mobile applications, pumps have usually been used to supply the pressure to the suction inlets of the pressure pumps.

Such auxiliary pumps can be connected to the main pressure fluid circuit various ways. In particular, if the direction of rotation of the main pressure pump is fixed, the pump need only have the capacity to supply the full quantity of hydraulic fluid at a pressure of several atmospheres gauge. If, however, the direction of rotation of the pressure pump may change, then check-valves are needed to interconnect the main lines of the auxiliary pump with the main pressure pump, the hydraulic fluid being supplied to the specific main line which is at a pressure commensurate with the outlet pressure of the auxiliary pump. The auxiliary pump then feeds not only Patented Dec. 8, 1970 the main pump but also supplies additional hydraulic fluid to compensate for leakage losses, but further supplies the required amount of fluid by-passed from the low pressure side for ventilation, cooling, and filtration. The auxiliary, or feed pump need supply only a fraction of the amount of fluid in the major fluid circuit.

Some applications require that the feed pump has a capacity commensurate with the capacity of the pressure pump. If this is required, the interconnection of the feed pump and the pressure pump is usually over rather large, high capacity check valves interconnecting the pressure line of the feed pump and the main lines of the pressure pump.

The interconnection of feed pump with the pressure pump can be over ducting or tubing. This is undesirable from an economic point of view, since the feed pump requires a separate drive and connection of interconnecting tubing is costly. It has therefore been proposed to combine the feed pump unit with the pressure pump unit in such a manner that the drive shaft driving the pressure pump also drives the feed pump, and the hydraulic con nections are formed directly within the housing of the entire assembly, or in connecting distribution blocks. Such arrangements have been constructed in which auxiliary pumps which supply a fraction of the maximum capacity of the main pump are combined with a pressure pump unit. Difliculties have, however, been encountered when the direction of rotation of the main pump unit for various models and types changes, since the suction and pressure side of the feed pump would likewise change. Thus, upon reversal of rotation of the drive of the main pump, a new type or re-built feed pump is necessary. It is possible to hydraulically compensate for reversal of direction of rotation, by providing two feed lines and two pressure lines, each supplied with check valves, and manually or automatically operable switch-over valves which connect the respective pressure chambers of the feed pump to the inlet line of the pressure pump, and to separate the suction side therefrom. Such switch-over and check-valve combinations are expensive and further decrease the pressure and capacity of the feed pump due to narrowing of the lines at the position of the check-valves.

Similar problems are encountered when the supply capacity of the auxiliary feed pump should match the total output capacity of the pressure pump. The advantages obtained by integrated construction of pressure and supply pump often have to be sacrificed to obtain sufficient space for large ducts and valves, since compact arrangement of fluid communication and the changeover valves frequently requires higher manufacturing costs if the direction of rotation of the pressure pump should change; thus, it is usually easier to provide the feed pump with an individual drive and to interconnect the feed pump with the pressure pump by means of ducting or piping.

It is an object of the present invention to provide a pump, particularly one suitable as an auxiliary or a feed pump for a pressure pump which is small, has a high pumping capacity, which is versatile, and which can be directly connected to a pressure pump regardless of the direction of rotation driving the pressure pump itself.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, the pump is built up of a group of stacked, aligned plates arranged about an axis of symmetry. A

drive shaft for a pump unit, preferably a gear pump, extends transverse to the plates, and the communication openings and inlet and outlet openings are so arranged about the axis of symmetry that, upon reversal right for left of some of the plates, or rotation of the plates about the drive shaft, inlet and outlet openings will match and be appropriate for a reversed direction of rotation. Thus, an auxiliary or feed pump element can readily be constructed to form a part associated with a pressure pump, to be secured to the pressure pump housing, with all individual plates being identical and adapted to be associated with a pressure pump regardless of its direction of rotation, and without requiring any check-valves or line switch-over valves.

The structure, organization and operation of the invention will now be described more specifically in the following detailed description with reference to the accompanying drawings wherein:

FIG. 1, in two parts as FIGS. 1a and 1b, illustrates a feed pump arrangement utilizing a gear pump, in perspective, exploded view, FIG. 1a illustrating the arrangement for a counter-clockwise direction of rotation of the drive shaft, and FIG. 1b illustrating the arrangement for clockwise direction of rotation;

FIG. 2, in parts 2a and 2b, illustrating a three-gear type gear pump, FIG. 2a being for counter-clockwise, and FIG. 2b for clockwise direction of rotation, in exploded, perspective view;

FIG. 3 is a longitudinal sectional view through a secondary gear of a gear pump; FIG. 3a is an enlarged sectional view through gear teeth of a secondary gear wheel; and FIG. 3b illustrates a side view and its projected end sectional view of a bearing stub for a secondary gear wheel constructed in accordance with FIGS. 3 and 3a.

FIG. 1 illustrates an auxiliary pump in the form of a gear pump, having two gear wheels. The auxiliary, or feed pump, can be secured to the base 1 of a hydraulic high-speed pressure pump, for example of the type illustrated and described in my co-pending application Ser. No. 776,469 filed Nov. 18, 1968, the disclosure of which is hereby incorporated by reference. The base of the hydraulic pressure pump 1 has the inlet and outlet ducts bored therein, as well as connections to the pumping unit and other lines and connections to supply and sump units which need not be described further in connection with the present invention.

The auxiliary pump, in accordance with the present invention, has a housing consisting of three parts, all in plate form. A suction plate 2, secured to a central plate 3 and an intermediate plate 4, are all arranged, in stacked alignment on the base of the hydraulic pump 1, for example by screws or bolts passing through holes 8, 8, 8" of the plates 2, 3, 4 and screwed into pressure pump 1. A suction opening 5 is bored through suction, or end plate 2. A central hole 6 forms a bearing bore; additionally, a bearing stub 7 is secured to the plate; suction hole 5, bearing hole 6 and stub 7 are arranged on an axis of symmetry of plate 2. Suction hole 5, at the side not shown in the drawings, can be adapted for connection to piping or other conduits to supply a pressure fluid, for example oil, to the feed pump.

Central plate 3 has an opening 9 therein in which a primary gear 10 is located. Gear 10 is secured on a drive shaft 11 which is formed with a coupling claw 12 at the end facing pressure pump 1. Claw 12, or any other coupling arrangement, is adapted to mesh with a drive shaft, or other source of rotary power derived from the drive to the main pressure pump 1. Primary gear 9 will thus rotate with the same speed as the pressure pump 1, and let it be assumed that the drive is in the direction indicated by arrow 17. A secondary gear 14, located in a gear notch 13, meshes with primary gear 10. Primary gear 10 itself is located in a primary gear notch 9. Plate 3 is further formed with a chamber-like opening 15 which interconnects the suction opening 5 in plate 2 with the suction side of the gear pump formed by gears 10, 14. Fluid entering through opening 5 and into chamber 15 will be supplied under pressure to the space 18 adjacent the gears. Space 18 is located at a position which matches a bore and stub connection 19 in the next, intermediate plate 4.

Plate 4 has a solid face 4' on the side directed towards plate 3 which is, however, recessed with respect to the side facing pressure pump 1 to form a ring-shaped channel 20 therein. A central bore 21, with a stub therearound, forms a bearing and guide for the drive shaft 11. A small stub 22 is secured in the ring-shaped opening 20 to provide direct communication of the pressure chamber 18 in plate 3 with a bore 23 in pressure pump 1. The fluid communication path in the base plate of pressure pump 1 is indicated by the broken lines. From opening 23, a duct or line connects to a filter, schematically illustrated at 24, and then to another duct opening 25 which communicates with a ring-shaped channel 20. From channel 20, fluid communicates with one or the other of connections 26, 27, and then over check-valves 28, 29, a duct leads to the suction or low-pressure side of the pressure pump 1.

Rotation to the gear pump in plate 3 is transmitted over the shaft 11, claw or clutch unit 12, to rotate the gear in the direction of arrow 17; if, however, pump 1 is arranged to be driven in a reverse direction, the very same unit as that illustrated in FIG. 1a can be used. Thus, if the direction of rotation is in accordance with arrow 17, as illustrated in connection with plate 3' in FIG. 1b, it is only necessary to reverse the central plate 3 left for right, and to bring it in the position shown at 3 in FIG. 1b. Intermediate plate 4 is brought into the position shown in FIG. lb at 4 by rotating the plate by 90 about the central axis of the pump.

It is not necessary that the pressure opening 18 communicates over a stub 22 with opening 23 in the pressure pump 1. If it is not necessary to have the fluid pass through filter 24, stub 22 can be omitted and the pressure fluid can communicate directly over hole 19 from pressure chamber 18 into the ring-shaped chamber 20, to communicate there with one of the two connections 26, 27 on the low-pressure side of the pressure pump. In such operation, openings 23, 25, and all the ducting in connection with the filter 24 can be omitted.

It is immediately apparent that the direction of rotation of the prime mover driving shaft 11 can be changed, and the feed pump re-arranged to accept the changed direction of rotation, without addition or subtraction of parts, and without complicated re-adjustment of elements, but merely by reversing plate 3 and rotating plate 4 over an angle which will bring opening 19 again in registration with pressure chamber 18.

The pump of the present invention can be made as a multi-gear pump, for example as a triple-gear pump. FIG. 2a illustrates a front or suction plate 30 on which are stacked a gear plate 31 and an intermediate plate 32, the assembly of all three plates being again secured to a connecting plate of pressure pump 1. FIG. 2a illustrates the arrangement for the direction of rotation as seen by arrow 48, while FIG. 2b illustrates the arrangement for the reverse direction, see arrow 48.

Suction flange 30 is formed with a central bore 33 to provide a bearing for the drive shaft of the central or main gear. A pair of bearing stubs 34 are symmetrically located about a vertical axis of symmetry; two suction openings 35 are located about a horizontal axis of symmetry. The suction openings 35 may be interconnected at the outside to be joined to a common suction line.

The central plate 31 has inlet chambers 35', 36, which have extensions 37, 38, extending up to the horizontal axis of symmetry of plate 31, to communicate with inlet openings 35 formed in plate 30. The pressure chambers 39, formed in plate 31 match the location of openings 41, 42, formed in the back wall 32' of intermediate plate 32. The back wall 32' defines, together with the front face of intermediate plate 32, when bearing against the bottom plate of pressure pump 1, a ring-shaped chamber 43. Fluid communication is established from ring-shaped chamber 43 over openings 44, 45, and check-valves 46, 47 (only schematically illustrated) with the low-pressure side of the pressure pump 1.

If the direction of rotation indicated by arrow 48 (FIG. 2a) is to be reversed, as seen in arrow 48', it is only necessary to reverse plate 31 left over right and bring it into the position shown at 31 in FIG. 2b; and further to rotate plate 32 over the axis of the shaft of the central gear by 90, in order to align holes 41, 42 with the changed position of pressure chambers 39, 4.0. Again, no parts of the pump assembly need be changed structurally, no parts need be added or removed, and no hydraulic connections at the inlet, or outlet side need be changed.

The feed pump of the present invention has been illustrated as a gear pump. In such gear pumps, it is customary to provide an arrangement to remove oil trapped between the meshing gear elements, in order to prevent operating noise or other undesirable operating conditions. Such arrangements customarily depend, however, on the direction of rotation so that, once associated with a pump, they are active only in a single direction of rotation, but ineffective and possibly damaging and detrimental to proper pressure differentials when the direction of rotation changes. In accordance with the present invention, pressure fluid trapped between the gear teeth can be removed by providing bores extending from the central shaft to the root, and partly to the tip of the gear teeth of the gear wheels. Thus, by mere reversal of the position of the secondary gears 49 on their stub shafts 7 or 34, respectively, trapped oil can still be removed regardless of direction of rotation.

Referring now to FIGS. 3, 3a and 3b, two rows of parallel bores 50 connect the central hub 51 with the space between a pair of adjacent teeth. The number of bores 50 corresponds to the number of teeth, or rather to the gaps between the teeth, and extend, as seen in FIG. 3a, to the roots of the teeth. As best seen in FIG. 3a, the bores 50 are not exactly on center with respect to the roots between the teeth, but are rather shifted laterally therefrom over towards the teeth themselves. Depending upon the direction of rotation, and that is, on the position, end over end of wheels 49 on stub shaft 7, or 34, the bores will face the gear teeth as illustrated in FIG. 3a, or, symmetrically opposite thereto. Thus, regardless of the direction of rotation, by reversal of the gear teeth 49 on stub shaft 7 or 34, trapped oil can still be removed.

The trapped oil which reaches the space of hub 50 is carried off by a relief 53 formed at the end points 52 of stub shafts 34 (not shown in FIG. 2a). The reliefs 53 are located on the ends 52 of the stub shaft in position to match the position of the bores 50, to permit escape of trapped oil.

Change ofthe direction of rotation thus requires only a very simple change in the relative arrangement of the parts forming the pump unit. Mere reversal of the plate on which the gears of the gear pump are retained, as well as reversal of the secondary gear elements themselves provides full supply of fluid with a changed direction of rotation as well as for proper removal of trapped pressure fluid, and without requiring any other additional changes in ducting or manufacturing. The feed pump of the present invention is thus particularly applicable for combination with pressure pumps constructed in accordance with the invention of the aforementioned patent application, or other pumps in which the direction of rotation can readily be changed without substantial re-working or re-arranging of the pressure pump unit. This is particularly true in wobble plate pumps, which can operate in either direction of rotation, requiring only change in the angular orientation of the wobble plate. Thepump 6 of the present invention, although generally useful in applications in which the direction of rotation of the prime mover is not invarient, is thus particularly applicable and useful in connection with rotary cylinder-wobble plate piston pumps.

I claim:

1. Modular hydraulic pump formed of a group of aligned plates secured together in stacked relation, said pump being adapted to be connected to a hydraulic pressure apparatus having a closure plate formed with suction openings at predetermined position thereon, said pump comprising:

a suction plate (2, 30) having a suction opening (5,

I extending transversely thereto, said suction plate having a center line and an axis of symmetry transverse to said center line;

a central bearing (6, 33) located on said center line and on said axis of symmetry, and a central gear (10) journalled in said bearing and located against the face of said suction plate;

secondary bearing means (10, 34) secured to said suction plate and located offset with respect to the cen. ter line and on the axis of symmetry, and a secondary gear (14) journalled on said secondary bearing means, in meshing engagement with said central gear;

a central plate (3, 31) having a central opening (9) surrounding said central gear and formed with a lobeshaped opening (13) surrounding said secondary gear, said lobe-shaped opening having extensions on both sides (15, 18) of said secondary gear, one side extension (15, 37, 38) providing for fluid supply to, and the other side extension (18, 39, providing for fluid removal from said secondary gear;

an intermediate plate (4), formed with a communicating opening (19) located at a distance from said center line equal to the distance of said other side extension of the lobe from said center line, said plate being formed with a ring-shaped chamber (20) extending around said center line and in fluid communication with said communicating opening (19);

an outlet plate (1) having outlet openings (26, 27)

communicating at random locations with said ringshaped chamber;

and means removing pressure fluid trapped between the teeth of the central and the secondary gears including (3) a pair of parallel, circumferential relief notches cut, adjacent each other, into the journal shaft (52, 7, 34) supporting said secondary gear and at least one bore extending from the root between adjacent teeth (49) of said secondary gear to the hub thereof to provide for fluid communication from between the teeth to the journal shaft regardless of direction of rotation of said secondary gear, and permit removal of fluid trapped between the teeth of of said gears.

2. Modular hydraulic pump according to claim 1 wherein said secondary bearing means includes a stub shaft secured to said suction plate; and said other lobe extension providing for fluid removal is located at a line defined by an angle of 45 from the center of said stub shaft with respect to the axis of symmetry, whereby, upon rotation of said intermediate plate (4) by an angle of said communicating opening will be brought in aligned position with said lobe extension upon reversal left for right of said central plate.

3. Modular hydraulic pump according to claim 1 wherein said pump is a doubled gear pump having a pair of secondary gears, a pair of stub shafts secured to said inlet plate, said stub shafts being located on a line passing through said axis of symmetry; and fluid communication opening symmetrically located with respect to said axis of symmetry formed on said intermediate plate.

4. Modular hydraulic pump according to claim 1 wherein said bore extending from the space between adjacent teeth to the hub of. the secondary gear is offset with re- References Cited UNITED STATES PATENTS Truesdell 103-126(U) Kleckner 103-126(U) Kinnucan 103-117(U) Osborne 103126(U) 8 2,659,314 11/1953 Wood 103-126(U) 2,665,639 1/1954 Svenson 103-126(U) FOREIGN PATENTS 359,508 10/1931 Great Britain 103-117(U) MARK NEWMAN, Primary Examiner W. J. GOODLIN, Assistant Examiner US Cl. X.R. 418--190 

